Retroperitoneal Fibrosis Workup

Updated: Sep 02, 2021
  • Author: Chandra Shekhar Biyani, MS, MBBS, DUrol, FRCS(Urol), FEBU; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Workup

Laboratory Studies

Blood study results in patients with retroperitoneal fibrosis may include the following:

  • Elevated erythrocyte sedimentation rate (ESR)
  • Raised C-reactive protein (CRP) level
  • Raised urea and creatinine levels (50%-75%)
  • Normocytic normochromic anemia
  • Polyclonal hypergammaglobulinemia
  • Raised alkaline phosphatase level (has also been reported as a marker [3] )
  • Antinuclear antibodies (ANA; present in 60% of cases) [4]

Urinalysis results are usually normal. Rarely, microscopic hematuria or pyuria is observed.

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Imaging Studies

Computed tomography (CT) scanning is the most frequently used imaging method for diagnosis and follow-up of retroperitoneal fibrosis. However, a number of other imaging methods can provide useful information. For example, positron emission tomography/magnetic resonance imaging (PET/MRI) has potential advantage for imaging small lesions, while offering reduced radiation exposure. [30] For complete discussion, see Retroperitoneal Fibrosis Imaging.

Plain radiography

Findings are nonspecific and usually due to the late complications. Abdominal films may show obliteration of the psoas shadow and an enlarged renal outline due to hydronephrosis. Features of ankylosing spondylitis or metastasis may also be visible.

Chest radiography may demonstrate pulmonary edema or fibrosis. Mediastinal widening may result from a soft-tissue mass associated with mediastinal fibrosis.

Intravenous urography

The classic triad consists of the following [1, 31] :

  • Delay of contrast material with unilateral (20%) or bilateral (68%) hydronephrosis

  • Medial deviation of the middle third of the ureters (see the image below)

  • Tapering of the ureter at the level of L4/L5 vertebrae

Up to 18%-20% of control subjects may show this triad. [32]

Intravenous urogram shows medial deviation of the Intravenous urogram shows medial deviation of the middle part of both ureters.

Medial deviation of the ureter may result from retroperitoneal neoplasm, aneurysm, and bladder diverticulum.

Retrograde pyelography

Retrograde pyelography may show features similar to those described above. In addition, it may demonstrate poor distensibility of the ureters, as depicted in the images below.

Retrograde ureterogram reveals smooth narrowing an Retrograde ureterogram reveals smooth narrowing and medial shift of the ureter.
Retrograde pyelogram demonstrates hydronephrosis. Retrograde pyelogram demonstrates hydronephrosis.

Retrograde pyelography delineates the pelvic calyceal anatomy and is usually performed prior to insertion of the stent to decompress the kidneys.

Interestingly, very little resistance is encountered during ureteric catheterization despite the extensive extrinsic fibrosis.

Lymphangiography

The retroperitoneal lymphatics are delicate and fine structures; therefore, they are more easily compressed by retroperitoneal fibrosis than by the adjacent blood vessels and ureters. Thus, lymphatic obstruction should precede ureteric compression.

Lymphangiography may show obstruction of lymphatic flow at L3/L4 level, opacification of collateral channels, nonvisualization of lymphatics above the L4 vertebra, and delay in passage of contrast through the iliac and para-aortic lymphatics. [33]

Ultrasonography

Ultrasonography is a simple noninvasive modality used to assess response to therapy. Findings may include the following:

  • On a sonogram, retroperitoneal fibrosis appears as a retroperitoneal, extensive, well-defined, hypoechoic mass centered over the sacral promontory.

  • The degree of hydronephrosis and hydroureter may vary.

  • Doppler ultrasonography has no role in differentiating benign from malignant retroperitoneal fibrosis. [34]

CT scanning

On unenhanced CT scans, retroperitoneal fibrosis appears as a plaque that is isodense with muscle and that envelops the aorta and inferior vena cava between the renal hila and sacral promontory and usually extends laterally to incorporate the ureters. Obliteration of the fat plane between the mass and the psoas muscle may be observed, as depicted in the images below.

Contrast-enhanced CT scan demonstrates a periaorti Contrast-enhanced CT scan demonstrates a periaortic soft tissue attenuating mass.
Noncontrast CT scan shows periaortic fibrotic reac Noncontrast CT scan shows periaortic fibrotic reaction associated with an inflammatory aortic aneurysm. Note bilateral ureteric stents.

Retroperitoneal hemorrhage, primary retroperitoneal sarcoma, metastatic deposits to the retroperitoneum, and retroperitoneal amyloidosis may show similar findings on CT scans. CT scan features that suggest malignant pathology include lateral displacement of the ureter, anterior displacement of the aorta, local bone destruction, and a large bulky lesion.

Elevation of the aorta from the spine is uncommon in benign retroperitoneal fibrosis. If present, it may be a sign of malignancy. [35]

After contrast injection, the plaque may show a variable degree of enhancement, depending on the stage of the disease. Enhancement is usually significant in the early active vascular stage. On the other hand, enhancement is poor in the late vascular stage.

Magnetic resonance imaging

Both benign and malignant retroperitoneal fibrosis have low-to-intermediate signal density on T1-weighted images and density on T2-weighted images that varies based on the disease stage. During the early stage, signal density is high because of high fluid content and hypercellularity. In contrast, late-stage disease has low T2 signal intensity as a result of avascular acellular fibrosis and decreased fluid content. [36] Steroid therapy may lead to similar changes because of decreased tissue edema.

Inhomogeneity of signal intensity on T2-weighted images may suggest malignancy; however, differentiation between benign and malignant retroperitoneal fibrosis on MRI is difficult, and biopsy is usually required to confirm the diagnosis. [25]

One study assessed delayed gadolinium enhancement ratios by comparing retroperitoneal fibrosis enhancement with that of psoas muscle. The dynamic enhancement ratio in acute retroperitoneal fibrosis significantly differed from the ratio in chronic retroperitoneal fibrosis. Dynamic gadolinium enhancement may be useful in differentiating newly diagnosed retroperitoneal fibrosis from treated chronic disease and may have a role in assessing disease activity, monitoring response to treatment, and detecting relapse. [37]

MRI has some advantages over CT scanning, including multiplanar capability, independence of renal function, and absence of radiation.

Positron emission tomography

Positron emission tomography (PET) scanning with 18F-fluorodeoxyglucose (18F-FDG) is a functional imaging modality that has proved useful in the evaluation of retroperitoneal fibrosis. 18F-FDG identifies areas of high glucose metabolic activity. Because inflammatory cells have an increased glucose uptake, high levels of glucose metabolism are seen in a retroperitoneal mass associated with retroperitoneal fibrosis if inflammation is present.

However, uptake of 18F-FDG by retroperitoneal fibrosis tends be lower than that by malignancy. A study of 18F-FDG PET/CT by Wang et al found that lesions of idiopathic retroperitoneal fibrosis displayed a lower frequency of high 18F-FDG uptake than retroperitoneal malignancies (P = 0.017) and a lower mean maximum standardized uptake value (SUVmax). [38]

No noninvasive method can reliably assess disease activity. However, 18F-FDG may be more reliable than acute phase reactants (ie, ESR, CRP) for monitoring the course of retroperitoneal fibrosis and response to therapy. [39, 40]  In addition, it can reveal other sites of disease (eg, thyroid, thorax) and may help to identify the most appropriate sites for retroperitoneal biopsy.

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Histologic Findings

In 1948, Ormond described two histologic features in retroperitoneal fibrosis: an inflammatory early stage and a chronic stage. [41] In the early stage, an inflammatory infiltrate contains macrophages, lymphocytes, plasma cells, and occasional eosinophils; neutrophils are generally absent. The macrophages are often lipid-laden and contain areas of perivascular lymphocytic infiltrate composed of T cells and B cells. Generally, tissue is highly vascular with numerous small blood vessels throughout. In the chronic stage, the tissue becomes avascular and acellular with scattered calcification and progresses to fibrous scarring. [42] Occasionally, surrounding structures are invaded by retroperitoneal fibrosis. Invasion of the large veins may cause fibrous thickening of the intima, resulting in complete occlusion. Periaortic lymphatics may be blocked within the mass. Submucosal edema and lymphocytic infiltration may be observed in the ureter.

Corradi et al (2007) recently reported the presence of CD20 and CD3 cells, IgG4 plasma cells, and subtle vasculitic activity in idiopathic retroperitoneal fibrosis. [43]

Malignant retroperitoneal fibrosis demonstrates the presence of scattered nests of malignant cells within the inflammatory infiltrate. Hodgkin disease and sclerosing retroperitoneal lymphomas are the most challenging differential diagnoses for the pathologist to exclude. In 2002, Wu et al recommended the use of immunostains such as c-Kit, Leu-M1, Ki-1, LCA, and kappa and lambda light chain. [44]

Table. Differential Diagnoses of Retroperitoneal Fibrosis [43] (Open Table in a new window)

 

Retroperitoneal Fibrosis

Retroperitoneal Lymphoma

Sclerosing Mesenteritis

Desmoid-Type Fibromatosis

Inflammatory Myofibroblastic Tumor

Well-Differentiated Liposarcoma Sclerosing Variant

Ureteral displacement

Medial

Lateral

 

 

 

 

Ureteral obstruction

~80%

~50%

Rare

Rare

Rare

Unknown

Aortic displacement

Rare

Anterior

 

 

 

 

Reactive perivascular lymphoid aggregates

100%

Absent

Variable

Rare

Variable

Present in the inflammatory type

Necrosis

Absent

Variable

Fat necrosis

Rare

Focal

Fat necrosis

Vasculitis

~50%

Absent

Absent

Absent

Absent

Absent

Clonality

Absent

Variable

Absent

Absent

Absent

Present

Β-catenin

Negative

Unknown

Negative

Positive in 90% of cases

Negative

Variable positivity

ALK-1

Negative

Usually negative

Negative

Negative

Positive in 50% of cases

Negative

CD-117

Negative in spindle cell component

Rare

Variable

Negative

Rare

Negative

Desmin

Negative

Negative

Variable

Rare

Usually positive

Rare

S100

Negative

Negative

Negative

Rare

Negative

Usually positive in the adipocytic component

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Biopsy

A wide spectrum of fibroinflammatory disorders can mimic retroperitoneal fibrosis on imaging. Management strategies are diverse and depend strongly on the histological diagnosis and extent of the disease. Histology and immunohistochemistry are required to confirm the diagnosis.

The amount of tissue harvested via core needle biopsy may not be sufficient for the histological diagnosis. Therefore, open biopsy can ensure a definite histological diagnosis and is traditionally performed. However, it is associated with significant morbidity. Laparoscopic biopsy is safe, minimally invasive, cost-effective, and useful in making therapeutic decisions for retroperitoneal masses.

Tissue for histologic diagnosis can be obtained under CT or ultrasonographic guidance. In a 1999 publication, Dash et al described fine-needle aspiration for the diagnosis of retroperitoneal fibrosis, but most clinicians prefer a Tru-Cut needle biopsy. [45] In 1998, Pfammatter et al performed transcaval retroperitoneal core biopsies and suggested that the technique may have a role in patients at high operative risk, especially if the results from standard biopsies are inconclusive. [46]

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